If you're in doubt, here are four ways to know you're old:

◆You wear your belt four inches below your chin.

◆ You sing the praises of reading glasses to everyone you meet.

◆ You read the calorie content of egg nog before you buy it. (You buy it anyway.)

◆ You are genuinely surprised that social media sites such as Facebook have been selling your private - tee hee - information.

Not one student in my Opinion Writing class at UNC was surprised at a revelation that had me lifting my jaw - and then my dentures - off the floor. Just as I was probably the only one in the classroom who's ever bought Metamucel or watched a Matlock marathon, I was also the only one shocked to find that one's internet viewing history - and possibly even conversations - are peddled to the highest bidder.

A student in that class told of a cellphone conversation she'd had with her boyfriend, a conversation in which he invited her to a wedding: within minutes of ending the call, ads for - what else? - dresses to wear to weddings began popping up on her phone.

Nobody born since J.T. left Kool & the Gang will be surprised to learn that our privacy has been compromised and that every site you look at on your phone or computer is looking back at you. Who knew that Facebook founder Mark Zuckerberg, among others, has been monetizing every bit of information about us?

Apparently everybody under 30 knew, that's who.

Yes, sweet, dorky, lovable Mark Z. in the trademark ratty T shirt and hipster hoodie isn't mainly interested in putting you in touch with your high school sweetums or amusing us with videos of cats jumping in and out of boxes. (Smirk if you want, but watching those things lowers your blood pressure quicker than Valsartan.)

Zuckerberg made his his billions by peddling your information - your friends, hobbies, likes and dislikes - to companies that could then direct at you, with military precision, ads meant to separate you from your dinero.

Zuckerberg and his Chief Operating Officer, Sheryl Sandberg, just admitted - after vociferously denying - that the company hired a company to dig up dirt to discredit critics, especially George Soros, the billionaire philanthropist who had the nerve to criticize Facebook as "a menace to society."

Do you reckon being spied upon by the company's henchmen will change his assessment?

If you missed that news, it's not entirely your fault.

As savvy politicians have done for ages, Facebook executives confessed to the skulduggery late on Thanksgiving Eve, when they knew editors and reporters were headed home for the holiday and the public's attention was on more pressing issues, such as "how many carbs are in cranberry sauce?"

To a generation coming of age in a post-9/11 world, the notion of privacy apparently seems as quaint as the pre-email pronouncement from the late Secretary of State Henry Stimson that "Gentlemen don't read each other's mail."

Just as everyone who has boarded a plane since the terrorist attacks expects to be patted down and mean-mugged by TSA agents, young people have seemingly made peace with the fact that - when it comes to Facebook - they are the product, not the consumer.

The city of San Francisco's supervisor is proposing removing the Zuckerberg name from a hospital - it got there because Mark and his wife donated $75 million to it.

Just goes to show: it's never a good idea to name a building after a living person - unless it's Dean Smith.

In the 1960s, a counterculture mantra went something like "Never trust a man in a suit."

If one-tenth of the abuses attributed to Facebook under Zuckerberg's leadership are true, future generations will be saying "Yeah, and dudes who wear ratty T shirts and hoodies aren't so honorable, either."